Electrical position indicating system



Jul} 2, 1946. ROTERS 2,403,152

ELECTRICAL POSITION INDICATING SYSTEM- Filed Nov. 2 1942 3 Sheets-Sheet l INVENTOR HE ERT G.ROTERS LATITUDE M GORRECTOR at CAM ATTORNEY H. c. ROTERS 2,403,152

ELECTRICAL POSITION INDICATING SYSTEM Filed Nov. 2, 1942 5 Sheets-Sheet 2 7 July 2, 1946.

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lNVENTOR HER RT C. ROTERS M w ATTORNEY July 2, 1946. Q ROTERS 2,403,152

ELECTRICAL POSITION INDICATING SYSTEM Filed Nov. 2, 1942 3 Sheets-Sheet 3 H93 OORRECTOR 42o CAM\ 7o 7| 4o POWER -FOLLOWUP GEAR BOX MECHANISM l4? VOLTAGE LOAD LOAD O (BEGULATOF? PAD PAD CENTRIFUGAL GOVERNOR 6 E l IL I TORQUE AMPLIFIER 75 74a 74 J T330 g20b 2| b 20 20c 200 am 2| INDICATOR INVENTOR HE ERT C. ROTERS BY ATTORNEY Patented July 2, 1946 ELECTRICAL PGSITION INDICATING SYSTEM Herbert G. Roters, Roslyn, N. Y., assignor to Fair- I child Camera and Instrument Corporation, a.

corporation of Delaware Application November 2, 1942, Serial No. 464,306

This invention relates to an electrical system for indicating the course of a mobile vehicle and, whileit is of general application, it is particularly suitablefor use in indicating directly on dials the distances covered by avehicle, such as anaircraft. in the north-south and east-west directions, either directly in miles or in degrees of latitude and longitude, respectively.

In the operation of mobile vehicles, it is often desirable to be able to obtain a continuous indication oi the position 0! the vehicle. This is particularly true in the case or shipsand aircraft which operate over great distances in which there are no objects from which bearings can be taken. It is particularly desirable to provide such a system which is rugged, stable, and easily adjusted, which gives direct readings of latitude and longitude, and which at the same time avoids errors frequently appearing in instruments of such a type which are frequently greatly aifected in their operation by variable operating conditions, such as fluctuations in the power supply, variations in ambient and local temperatures, and the like.

It is an object of the present invention, therefore, to provide a new and improved electrical system for indicating the course of a mobile vehicle which realizes one or more of the abovenamed advantages and which gives a direct indication oi' the distance covered by the mobile vehicle either in miles or degrees of latitude and longitude. I

It is another object of this invention to provide a system'of the type described, in which the errors usually occurring in instruments of the type are largely self-compensating.

In accordance with the inventionan electrical system for indicating the course of a mobile vehicle comprises means for generating a primary alternating current electrical signal and two secondary alternating current electrical signals, togetherwith means for varying the phase of the primary and secondary signals relative to each other in accordance with the direction or the course of the vehicle. The system also includes a pair of integrating indicating means 11 Claims. (Cl. 235-61) the electrical characteristic of the secondary Signal comprises means for shifting the phe' cf 29 output signal of the variabiemhase g The preferred system includes a pair, of two'- phase eddy current motors each having a first winding excited from thereference generator and a second winding, the second windings being excited from different windings of the variablephase generator, while north-south and eastwest integrating indicating devices are individually driven by the motors. The control of the integrating devices in accordance with velocity of the vehicle is effected either by vari ably loading the eddy current motors, as by eddy current brakes coupled thereto and excited by a voltage variable in accordance with the velocity of the vehicle. Alternatively, such control may be eflected by means for varying the amplitude of one of the primary and secondary signals as applied to the eddy current motors in accordance with the velocity of the vehicle.

The control in accordance with the velocity of the vehicle may be introduced either manually or automatically by a power position repeater operated from an air-speed indicator. ation in the electrical characteristic of the primary and secondary signals relative toeach other also may be effected either manually or automatically by a power compass either directly or through a position repeating system.

For a better understanding of the present invention, together with other and further objects hicle;

thereof, reference is had to the following description taken in connection with the accompanying drawings; and its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 is a diagram, partially schematic, or a complete electrical system for indicating the course of a mobile ve- Fig. 2 is a cross-sectional view of a combined eddy current motor and brake suitable for use in the system of Fig. 1; Fig 3 is a circuit diagram, partially schematic, of a modified form of the system of Fig. 1 in which the control in accordance with the velocity of the vehicle is introduced into the excitation oi. the eddy curjointly energized by the primary signal and in rent motor rather than the brake; while Fig, 3a is a circuit diagram of a modified form of the reference signal generator of Fig. 3.

Referring now to Fig. 1 of the drawings, the

electrical indicating system there represented includes'a two-phase alternating current generator l0 comprising means for generating a primary electrical signal and a two-phase alternating current generator ll comprising means for generating two secondary electrical signals. The rotors of the two generators l0 and H are mounted on a common shaft l2 driven by a suitable constant speed source, such as a direct current motor I3 energized from direct current supply terminals ll through a voltage regulator H5.

The vari The motor i3 is provided with a centrifugal governor i3, or the equivalent, operating on a field resistor I! of the motor i3 to regulate closely the speed of the motor i3 and generators i3 and ii.

The generator it may be referred to as a fixed-phase or reference generator, as the phase 3 no! its output voltage is constant, while the output signal of the generator ii, which is a variablephaee generator, can be manually adjusted by means of a suitable mechanism It for angularhl rotating the stator of the generator, this mechaninn i3 constituting means for varying an electrical characteristic, that is, the phase of the output signals of the generator ll relative to that of the pneratcr ilin accordance with the direction of the course of the vehicle, the individual two-phase output signals being varied in accordance with the north-south and east-west components of the course of the vehicle. The generstore it, .i i, themotor i3 and its associated apparatus, and the adjusting mechanism is may all be of conventional form. The generators iii and ii comprise permanent magnet rotors or held members I30 and lid, respectively, and twophase armature windings. Since they are operated at constant speeds, they generate signals of substantially constant amplitude.

The system also includes a pair of integrating indicating means comprising a pair of polyphase alternating current motors, preferably two-phase eddy current motors 23 and ii. The motors 33, II are individualLv energized by the two secondary signals, that is, from the two phases of generator ii, and are operable at speeds variable in accordance with the electrical characteristic, specinoaliy the phase, thereof. Specifically, the motors 33, II have their respective phase windings 33a and lid excited from one phase of the reference generator i3, and have respective second wlndnigs 33b and lib excited from different phase windings of the variable-phase generator ll. Since only one phase of generator i3 is loaded, a

dummy load I. is preferably connected across the 3 other phase to maintain the load symmetrical. The exciting circuits of the windings of themotors 33 and ii are preferably tuned approximate- 1y to resonance by means of the series condensers 33, 33a and 33, 33a, respectively. The motors. 23 and II are also provided with auxiliary means associated with each motor for overcoming the friction load thereon and including means responsive to the direction of rotation thereof for reversing the sense of action thereof. This auxiliar! means comprises the pairs of reversely acting shaded coils tic, 33d and He, lid, respectively, the circuits of which are selectively closed by friction clutches 34 and II, respectively, driven by the motors, and switches 33 and 31, respectively, which are responsive to the direction of rotation of the motors.

The motors 23 and ii are provided with shafts 33 and 33, respectively, which are connected to operate integrating indicating devices such as the latitude and longitude indicators 3|, 3|, respectively, which may be of the conventional watthour clock or cyclometer type, for indicating the elapsed distances in the north-south and eastwest directions in minutes and degrees. The indicators II and 3i are provided with suitable reset mechanisms 33a and 3 la.

In order to modify the indications of the indionto" 33 and 3| in accordance with the velocity of the vehicle, there is provided means for controlling the action of the integrating means comprising these indicators in accordance with the velocity of the vehicle. In the system of Fig. 1, this is accomplished by means for variably loading the motors to control the action of the motors in accordance with the velocity of the vehicle. To this end there are provided eddy current brakes 33 and 33 attached to the shafts 23 and 23 of the motors 33 and 2 i, respectively, these brakes being provided with exciting field magnets 33a and 33a, respectively, having windings 32b and 33b. This controlling means also includes means for developing a voltage variable in accordance with the velocity of the vehicle, for example, a direct current generator 3t mounted on the shaft l2 and driven by the motor i3, and an adjustable resistor 31. The generator 34, windings 32b, 33b, and resistor 31 are all connected in a single series circuit so that the wind- I ings 33b, 33!; are excited by and responsive to such variable voltage. Connected across the exciting windings 32b and 33c are resistor-attenuator networks 35 and 36, respectively, including adjustable resistor elements so connected as to regulate the current through the windings 33b and 33b without materially modifying the resistance of the circuit as a whole. Connected in series with the generator 34 and the windings 33b and 33b is an adjustable resistor 31 adjustable by means of a manually operated crank 33 through a primary shaft 39, a linear corrector cam 30, and a secondary shaft 3 i. The corrector cam 40 is effective to establish a linear controlling action on the integrating indicating devices 33, 3 i. Mounted on the shaft 39 may be included also a pointer 42a of an indicator 42 for reproducing the setting of the speed indicator of the vehicle. The linear corrector cam 30 may be of any wellknown conventional type which will reproduce an original angular motion with an angular correction within given limits for each position of the input shaft. One well-known form comprises a flexible helical spring wound on a series of screw-adjusted dogs supporting it at spaced intervals, together with a follower roller operating on the periphery of the helical spring and driving the output shaft through a crank arm and a step-up-ratio gearing.

In order to compensate the indication of the longitude indicator 3| in accordance with the latitude of the vehicle, there is provided a means responsive to the north-south integrating means for compensating the east-west integrating means in accordance with the latitude of the ve hicle. This may comprise a latitude-corrector cam 33 actuated by the north-south or latitude indicator 33 by a 2:1 step-up gearing 44 and a follower roller 43 mounted on a pivoted link 33 which is effective to adjust the radial position of the field magnet 33a of the eddy current brake 33.

A cross-sectional view of a combined eddy current motor and eddy current brake suitable for use in the system of Fig. l is illustrated in Fig. 2 of the drawings. This device comprises a cupshaped eddy current motor rotor 53 and a cupshaped eddy current brake rotor I mounted on a common shaft 53 pivoted at opposite ends on the stud pins 53 and 34 supported in the opposite ends of the casing 33. The eddy current 1110- tor comprising the rotor 33 includes also twophase exciting windings, one phase of which comprises the coils i3 and I! mounted on a laminated core structure 58 supported within the easing 55 and including an annular laminated core portion 59 supported on the stud pin and forming with the core 58 a narrow annular air gap in which the rotor on rotates. CO-Operating with the brake rotor Si is an exciting winding 80 mounted on an insulating bushing 8| supported on the stud pin 54, Surrounding the brake rotor 5| is an annular magnetic yoke 62. Mounted within the rotor ii is a magnetic armature forthe form of a. sleeve 6| axially adjustable along the stud pin 54 by means of a pin-and link mechanism 65, adjustment of the core members ll, 64

relative to rotor 5| efiectively adjusting the flux linkage between the core members and the rotion proportional to torque is effected by means of the eddy current brakes I2, 3! which produce retarding or damping torques exactly propertional to speed and so give the desired result, provided that the speeds of the motors-mellow compared to their synchronous speed and provided that there is no appreciable friction load. The counting is done by the integrating devices 30 and II and, by utilizing appropriate geenra tios in these counters, they may be fin--1" dicat directly in miles the distance covered, that 1 is, the position of the-vehicle relative to the ing point.

In a p'referredembodiment, it is desired to indicate the position of the vehicle in minutes and degrees of latitude and longitude. Since the parallels of longitude are more clearly spaced for higher latitudes, the longitude indicator 5: is

compensated by means of the latitude-corrector cam 43 which adjusts the exciting magnet 33a of the brake 33 to vary its eflect on the eddy our tor 5i while maintaining the magnetic field, and

thus the exciting current, substantially constant.

Corning now to the operation of thesystem represented in Fig. l, the generators l0 and II are driven at substantially constant speed by themotor l3 so that both the primary or reference alternating current signal and the secondary alternating current signals are maintained at sub stantially constant frequency and amplitude. The phase of the signal output of the generator HI is maintained constant, while that of the .output signal of the variable-phase generator, H is manually adjusted in accordance with the direction of the course of the vehicle by the mechanism ll.

One phase of each 01' the motors 20, 2| is excited Irom one phase of the generator II; the other phase windings of the motors 20, II are excited irom different phase windings of the generator II. It is a characteristic of this type of eddy current motor that the torque developed is proportional to the product of the currents in the two-phase windings and the sine of the phase,

angle between these two currents. The principle of operation is exactly that of the integratrent brake. In case the combined eddy current motor and brake of Fig. 2 is utilired in the sys-- tem, the adjusting link I! is operated by the latitude-corrector cam. The shape of this cam is determined experimentally from a calibration of the speed of the motor II as a function of the radial position of the magnet "a, which is usually a nonlinear'function. The term "position 0! the vehicle," as used in the specification and appended claims, is, therefore, intended to describe the indication of the integrating devices either with the latitude corrector cam, in which relative position is indicated, or without the corrector cam, in which case absolute-position is indicated. I .1 i

In order to control the-action of theiiitegrating indicating means with the clusive. The retarding torque oi the eddy cur--- rent brake of the type .ot' tlie units 32, 82 is proing watt meters used for the commercial meas- M, respectively. Then, for any given course of the vehicle, the phase angle between the current supplied from generator H to one of the motors, for example, the motor 20 associated with the latitude indicator, and that supplied by generator ID will be 90 degrees minus the courseangle and the torque developed by the latitude-indicator motor will be proportional to the sine of 90 degrees minus the course angle, which is the north-south or latitude component. Similarly, the torque developed by the longitude-indicator motor 2| will be proportional to the sine of the course angle, which is .the east-west or longitudinal component of the vehicle motion.

In order to translate these torques into latitude and longitude readings, it is necessary to integrat them as functions of time. This is done by causing the motors 2|, II to rotate at speeds proportional to their respective driving torques portional tothe square ofthe exciting current. "Hence, .for the torquetobe varied linearly with velocityzof the vehicle, the exciting current 1: shouldv vary inversely proportionally to the squareeroot oi" the vehicle velocity. This relationship is approximated by the variable series resistor 31, which results in a velocity-excitation current characteristic which is substantiallyhycurrent brake I2 is then-so adjusted as to give the proper speed as determined by the indicator 3! and a stop watch. Similarly, with the generator adjusted to a position corresponding to a due east course. the resistor-attenuator network a is so adjusted as togivethe P p r speed as determined by the indicator II and a stop watch. The attenuators II and 4| are now locked in this position and subsequent calibrations for different settings of the velocity indicator 42a are carand counting their total revolutions. Such rotaried out by adjusting thecorrector cam 40 to give moans:

theeorrespondingbrakespeedsiorduenorthand eastcourses. As was stated above, the desired relationship between the torques oi the motors ll, 2i. and their speeds, as determined by the eddy current brakes 32. I3. is obtained only with a negligible iriction load. Such iriction load is avoided by the use oi theshading coils 10c, ild and Iic, lid associated with the motors II. II, respectively. Thecircuitsoithetwocoils oi eachmotorare seiectiveiyclosedby the associated one oi the switches II, II and act reversely on their assoelated eddy current rotors. each being eiiective to overcome the iriction load oi the motor in a given direction oi rotation. The iriction clutches 2i and 3! associated with the motors it. ii are elective to select the shading coil in each case to overcome the iriction load in the particular direction oi rotation which. oi course, changes with the cum in the direction oi the course oi the vehicleon either side oi the east-west and northsouth directions.

The ioregoing system has a number oi advantages. It automatically compensates, to a. large degree. ior changes in speed oi the driving motor it due to residual fluctuations in the power supply not eliminated by the voltage regulator ii and governor it. These residual speed changes are. moreover. minimized by the iact that the loads on generators II and II are constant. The voltages oi the generators II and II vary directly with speed. These voltages are applied to the eddy current motors 2., II. the torques oi which vary with the square oi the applied voltage but are independent oi the corresponding irequency change provided that their circuits are substantially resistive. This is procured in this case by broadly tuning the motor circuit by 'means oi the condensers II. I! and 22a, 23a so that they have a substantially constant and resistiveimpedance over the range oi irequencies encountered in normal operation. On the other hand. the voltage developed by the generator N, which excites the magnets 32a, 32b oi the eddy current brakes 32. 88. respectively. also varies directly with the speed oi the driving motor ll. while the drag; oi the brakes I2, 18 vary as the square oi the excitation. Thus the torques oi the motors 2|. 2i and the drags oi the brakes ll. a vary proportionately with variations in the speed oi the driving motor II and are seli-,

compensating.

The system is also self-compensating ior changes in ambient temperature. Thus the resistances oi the motors and generators, which are'primarily copper circuits. vary directly with temperature and the currents in these circuits varyinversely with resistance and thus inversely with temperature. Ii the entire brake circuit. including the adjustable resistor 31, is also a copper circuit, its resistance varies in a similar manner and compensates the variation oi the resistance oi the motor generator circuits. In the case oi local heating oi particular elements. such as the adjustable resistor I1 and the exciting windings lib and Nb oi the eddy current brakes. any nonlinearity due to the change in resistance in these circuits is compensated by the linearity-correcting cam 40.

The dummy load I. is eflective to balance the load on the generator Ill so that the loads on both generators II and ii are symmetrical and wnstant, thus preventing any change in the alternating current output or phase angle 01 these generators due to a variable load. In addition,

since the loads on the generators II and II are constant, they can be designed ior minimum size with heating rather than voltage regulation as a limitation on design. The use oi the variable excitation oi the eddy current brakes ll, 31 to introduce the velocity component oi the vehicle into the system permits an easy initial adjustment oi the system at its normal operating speed by varying the attenuator networks II, It shunting the exciting coils 82b and Nb, respectively. These attenuator networks are so designed that their adjustments are independent oi each other and do not ai'iect the resistance oi the circuit as a whole or the current in the remainder oi the circuit so that they can be adjusted independently oi each other.

There arecertain adjustments oi this system which contribute to the maximum accuracy under various operating conditions. 'The tuning of the several phase windings oi the generators II and ii to the operating range oi ire'quencies by the condensers 21, 21a, 28. 13a to impart a substantially'constant and resistive impedance to the generator circuits also results in a closevoltage regulation oi these generators. In order to prevent any appreciable reaction irom the stator windings on the permanent magnet rotors oi the generators II and ii. these rotors are we!- erably made oi high retentivity alloy steel. such as that commercially available under the trade name "Alnico. and the generators are made with a relatively large air gap and very strong rotor magnets.

The system oi Fig.3 is similar to that oi Pig. 1 except that the velocity oi the vehicle and the direction 0! its course are introduced automatically. rather than manually. and that the velocity oi the vehicle controls the system by variation oi the excitation oi the eddy current motors II and ii by variation oi the amplitude oi the output oi the reierenoe generator ll, rather than by variation oi the excitation oi the ed y current brakes. Otherwise the system oi Pig. 3

is similar to that oi Fig. 1 and corresponding elements are identified by the same reierence characters. This system includes means responsive to the velocity oi the vehicle for varying the amplitude oi the signal output oi generator II as applied to the integrating indicating means. This means comprises the velocity indicator 2 having a pointer 42a coupled to a power followup mechanism which, through a suitable gear box 1i, actuates the linearity-correcting cam II. The output shait 4i oi the cam It operates an adjustable arm Ila oi an autotransiormer I2 excited across one phase oi the reiere'nce generator II. The secondary or output signal irom the adjustable autotransiormer I1 is applied to the phase windings 20a, Ila oi the motors 2|, 2|, respectively. A load pad 13 is connected across the secondary portion oi the autotransiormer 12 to minimize variations in load on the generator ll. 7

In the system oi Fig. 3, the adjustment oi the stator oi the generator Ii is eiiected by means responsive to the direction oi the course oi the vehicle for varying the phase oi the-secondary signals relative to the primary signals and comprising a power compass having a shait "a operating a torque amplifier 14 which. through a shait It. operates the gearing It associated with the stator oi the generator ii. In the system oi Fig. 3, the eddy currentbrakes I2, 33 oi Fig. l are replaced by brakes II, II having associated permanent damping magnets I'Ia, Ila, respectively. In-order initially to calibrate the operation of the system, the magnets 11a, 18a are provided with magnetic shunts 11b, 18b, respectively,- adjustable by screws 11c, 180, respectively.

In general, the operation of the system of Fig. 3

is similar to that of Fig. 1 except thatthe signal output from one phase of the reference generator I is applied to the phase windings 20a, Zia of the motors 20, 2| and is varied in amplitude in accordance with the velocity of the vehicle by means of the adjustable autotransfonner 12. As a result, the driving torques of the motors 20, 2| vary with the velocity of the vehicle, while the damping torques exerted by the brakes I1, 18 remain substantially constant, so that the speed of the indicating system varies directly with the velocity of the vehicle and the integrated distance covered is indicated by means of the indicators 30, 3| as in the system of Fig. 1.

In order to attain maximum accuracy in the system of Fig. 3, it is desirable that the voltage of the outputs and the phase angle between the two-phase currents of the generators l0 and II vary only in response to variations in the velocity and course of the vehicle and not in response to variations in the loads on these generators. Therefore, since the load on the generator I0 is variable, there is provided the load pad I3 which tends to maintain the load on the generator more constant. At the same time, the impedances of the generators Ill and I l are preferably made low compared to those of their connected circuits. .The adjustable magnetic shunts 11b and 18b provide means for readily adjusting the initial calibration of the system as well as for correcting for variations in the magnetic field of the permanent magnets Ha, Ha with age.

In Fig. 3a there is represented a modification of the arrangement of Fig. 3 for introducing the velocity factor into the system. In this case, the

elements 42, 10, ll, 40, 4|, and 12 are eliminated and the output of the reference generator 19 is varied in accordance with the velocity of the vehicle by providing it with a field winding 80 which is excited from an air-speed generator 8| through a resistor 82. The air-speed generator BI is driven in a conventional manner such that its speed is proportional to the true air speed, for example, by a propeller as shown. If the generator 8| is provided with a constant field, for example, a permanent magnet field, its output voltage is proportional to true air speed. In order to compensate for variations in the resistance of the windings oi the air-speed generator and of the generator 19 with variations in temperature, a voltage derived from one phase winding of the generator 19 is rectified by the rectifier 83, shown schematically as of the copper oxide type, and fed back across resistor 82 in the field circuit of the generator. The generator 19 of Fig. 3a and its associated circuit elements may be substituted for the generator ID of Fig. 3 by connecting the terminals A, B of Fig. 3a to the corresponding terminals of Fig. 3. The operation is otherwise similar to that of Fig. 3.

This system has the advantage that the impedance of the circuits of generator 19 remains constant and independent of the velocity and, hence, there is no possible phase shift between the outputs of generators l9 and H as the velocity changes. This permits both generators 19 and H to be designed with heating as a limitation. If the circuits of these generators are made inductive, their current outputs are relatively independent of small changes in voltage produced 10 by changes in the speed of the driving motor, because the reactance of the generator circuit decreases directly with the motor speed in the same proportion as the voltage decreases. In this manner, compensation for residual changes in generator speed is obtained.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such dhanges and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary alternating current electrical signal and two secondary alternating current electrical signals, means for varying the phase of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, a pair of integrating indicating means jointly energized by said primary signal and individually energized by said secondary signals and responsive to the relative phase thereof, and means for controlling the action of said integrating means in accordance with the velocity of said vehicle, whereby each of said integrating means indicates the position of said vehicle in one direction.

2. An electrical system for indicating the course of a mobile vehicle comprising, a pair of alternating current signal generators, a common driving means for said generators, one of said generators having a two-phase output winding, means for shifting the phase of the output signal of one of said generators relative to that of the other in accordance with the direction of the course of said vehicle, a pair of integrating indicating means individually energized from the phase windings of said one generator and by the other of said generators and responsive to the relative phase of output signals thereof, and

means for controlling the action of said integrat- H ing means in accordance with the velocity of said vehicle, whereby each of said integrating means indicates the position of said vehicle in one direction.

3. An electrical system for indicating the course of a mobile vehicle comprising, a fixedphase reference generator, a variable-phase twophase generator, a common driving means for said generators, means for shifting the phase of the output signal of said variable-phase generator in accordance with the direction of the course of said vehicle, a pair of two-phase eddy,

current motors each having a first winding excited from said reference generator and a second winding, said second windings being excited from different windings of said variable-phase generator, north-south and east-west integrating indicating devices individually driven by said motors, and means for controlling the action of said motors in accordance with the velocity of said vehicle, whereby said integrating devices indicate positions of said vehicle in the north-south and east-west directions, respectively.

4. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary electrical signal and two secondary electrical signals, means for varying an electrical characteristic of said primary and moans secondary signals relative to each other in accordance with the direction of the course of said vehicle, a pair of motors individually energized by said secondary signals and operable at speeds variable in accordance with variations in said electrical characteristic thereof, north-south and east-west integrating indicating devices individually driven by said motors, and means for variably loading said motors in accordance with the velocity of said vehicle, whereby said integrating devices indicate positions of said vehicle in the north-south and east-west directions, respectively.

5. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary electrical signal and two secondary electrical signals, means for varying an electrical characteristic of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, a pair of motors individually energized by said secondary signals and operable at speeds variable in accordance with variations in said electrical characteristic thereof, north-south and east-west integrating indicating devices individually driven by said motors, means for developing a voltage variable in accordance with the velocity of said vehicle, and means responsive to said voltage for variably loading said motors, whereby said integrating devices indicate positions of said vehicle in the north-south and eastwest directions, respectively.

6. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary electrical signal and two secondary electrical signals, means for varying an electrical characteristic of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, a pair of motors individually energized by said secondary signals and operable at speeds variable in accordance with variations in said electrical characteristic thereof, north-south and east-west integrating indicating devices individually driven by said motors, means for developing a voltage variable in accordance with the velocity of said vehicle, and an eddy current brake coupled to each of said motors and excited by said voltage, whereby said integrating devices indicate positions of said vehicle in the northsouth and east-west directions, respectively.

'I. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary electrical signal and two secnndary electrical signals, means for varying an electrical characteristic of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, a pair of motors individually energized by said secondary signals and operable at speeds variable in accordance with variations in said electrical characteristic thereof, auxiliary means associated with each of said motors for overcoming the friction load thereof and including means responsive to the direction of rotation thereof for reversing the sense of action thereof, north-south and east-west integrating indicating devices individually driven by said motors, and means for variably loading said motors in accordance with the velocity of said vehicle, whereby said integrating devices indicate positions of said vehicle in the north-south and east-west directions, respectively.

8. An electrical system for indicating the course of a mobile vehicle comprising, a fixed-phase ref- 12 erence generator, a variable-phase two-phase generator, a common driving means for said generators, means for shifting the phase of the output signal of said variable-phase generator in accordance with the direction of the course of said vehicle, a pair of two-phase eddy current motors each having an eddy current rotor, a first winding excited from said reference generator and a second winding, said second windings being excited from different windings of said variable-phase generator, a pair of reversely-acting shading coils associated with each of said rotors for overcoming the friction load thereof, and means responsive to the direction of rotation of each of said motors for selectively energizing its associated shading coils, north-south and east-west integrating indicating devices individually driven by said motors, and means for controlling the action of said motors in accordance with the velocity of said vehicle, whereby said integrating devices indicate positions of said vehicle in the northsouth and east-West directions, respectively.

9. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary electrical signal and two secondary alternating current electrical signals of substantially constant amplitude, means for varying the phase of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, a pair of integrating indicating means Jointly energized by said primary signal and individually energized by said secondary signals and responsive to the relative phase thereof, and means for varying the amplitude of one of said primary and secondary signals as applied to said integrating means in accordance with the velocity of said vehicle, whereby each of said integrating means indicates the position of said vehicle in one direction.

10. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary electrical signal and two secondary electrical signals, means for varying a first electrical characteristic of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, means for varying the second electrical characteristic of at least one of said primary and secondary signals relative to the other in accordance with the velocity of said vehicle, a pair of integrating indicating means jointly energized by said primary signal and individually energized by said secondary signals and responsive to both of said electrical characteristics thereof, whereby each of said integrating means indicates the position of said vehicle in one direction.

11. An electrical system for indicating the course of a mobile vehicle comprising, means for generating a primary alternating current electrical signal and two secondary alternating current electrical signals, means for varying the phase of said primary and secondary signals relative to each other in accordance with the direction of the course of said vehicle, means for varying the amplitude of at least one of said primary and secondary signals relative to the other in accordance with the velocity of said vehicle, a pair of integrating indicating means Jointly energized by said primary signal and individually energized by said secondary signals and responsive to the relative phase and amplitude thereof. whereby each of said integrating means indicates the position of said vehicle in one direction.

HERBERT C. ROTERS. 

